1. Field of the Invention
The present invention relates to an automatic speed control apparatus for vehicles and, more particularly, to the improvement of an automatic speed control apparatus for vehicles which enables speed control at the beginning of constant-speed travel of a vehicle (hereinunder referred to "cruise") with quick responsiveness by using a cruising actuator sensor which can detect the amount of working of the cruising actuator itself.
2. Description of the Prior Art
The running speed of a vehicle is generally controlled by the driving force from the accelerator or accel pedal worked by the driver, but in the case of continuously driving the vehicle at a constant speed for a long time, automatically controlled cruise is useful which is so controlled as to automatically open and close the throttle valve at a preset speed. Such a control apparatus is mounted on vehicles as an automatic speed control apparatus and is helpful in lessening the fatigue of the drivers.
In such an automatic speed control apparatus, the delay in control at the beginning of cruise often irritates the driver and it is a common problem that if a delay in control occurs when the driver selects cruise by the set switch, the speed is temporarily reduced, thereby hindering the smooth running of the vehicle.
The delay in control is mainly caused by a trouble in the link mechanism which transmits the driving force of the actuator to the throttle valve. When the link mechanism requires a long route, for example, when the cruising actuator directly drives the accel pedal, the route of the link mechanism to the throttle valve becomes very long and since the link mechanism is heavy, even if the cruising actuator is operated swiftly by a predetermined amount of working, the play in the link mechanism directly leads to the delay in control of the throttle valve, thereby bringing out the above-described problems.
In a conventional automatic speed control apparatus, the play in the link mechanism from the cruising actuator to the throttle valve is stored in a control unit as a presupposed constant value, and when cruise running is selected, the thus-determined initial amount of offset is provided for the cruising actuator in order to cancel the play in the link mechanism.
The amount of offset, however, is different in vehicles and changes with time even in the same vehicle due to the frictional resistance of the link mechanism or the like. Practicable correction is therefore beyond the capabilities of the above-described conventional automatic speed control apparatus, in which the amount of offset is set at a presupposed constant value.